1. Field of the Invention
The present invention relates to a display device having an inverted staggered thin film transistor in each of a driver circuit and a pixel portion.
2. Description of the Related Art
As one kind of field-effect transistors, a thin film transistor in which a channel formation region is formed in a semiconductor layer formed over a substrate having an insulating surface is known. Techniques in which amorphous silicon, microcrystalline silicon, or polycrystalline silicon is used for semiconductor layers used in thin film transistors have been disclosed. A typical application of a thin film transistor is a liquid crystal television device in which the thin film transistor has been put to the practical use as a switching transistor for each pixel included in a display panel.
Further, for reduction of the cost of a display device, there is a display device of which the number of external components is reduced and in which thin film transistors formed using amorphous silicon or microcrystalline silicon are used for a gate driver (see Patent Document 1).